This invention relates to implantable electrical apparatus for stimulating body organs and has particular relationship to such apparatus which includes a catheter for connecting the electrical output of the apparatus to the organ to be stimulated. In the interest of dealing with this invention concretely so that it will be better understood by those skilled in the art, the description of this invention is predominately directed to heart pacers. While this invention is uniquely applicable to heart pacers, it is also applicable to other organ-stimulating apparatus and to the extent that it is embodied in such apparatus, such embodiment is within the scope of this invention.
A typical implantable organ-stimulating apparatus is a heart pacer of the type described in Purdy, et al. U.S. Pat. No. 3,866,616. Such a heart pacer includes a container within which an electrical circuit is sealed. This electrical circuit produces electrical pulses which stimulate the heart of the host. The stimulating pulses are supplied to the heart through a catheter connected between the circuit and the heart. The catheter has a terminal (or, in the case of a bi-polar pacer, a pair of terminals,) which is inserted laterally in a terminal block that communicates with a cavity. The terminal is held by a set-screw which passes through the cavity and is screwed into the terminal block and becomes cold welded to the terminal. To preclude electrical leakage through body fluids, the terminal block must be sealed against the penetration of body fluids. The seal is inserted in the cavity. The securing of the terminal of the catheter and the necessity of sealing the cavity has presented a serious problem to the surgeons who implant the heart pacers. To suppress the penetration of body fluids into the terminal block some surgeons adopted the practice of plugging the opening in the cavity in which the set-screw is inserted with a silicone-rubber cement during implantation. This expedient has not proven entirely satisfactory. Another practice which has been preferred is to plug the opening in the cavity with a silicone-rubber plug from whose periphery an O-ring extends. U.S. Pat. No. 4,037,277 granted July 26, 1977 to Frederick J. Shipko for Surgical Tool and assigned to CORATOMIC, INC. is directed to a heart pacer including a surgical tool for inserting the set-screw and the plug in this practice. While the Shipko teaching has materially improved the practice of securing the catheter terminal and sealing the cavity into which it extends, surgeons continue to experience difficulties in carrying out this operation. A source of frustration experienced by surgeons is that the set screw and plug are small and at times one or the other is lost on or near the operating table.
It is an object of this invention to overcome the above disadvantages of past practice in implanting heart pacers and other organ-stimulating apparatus and to provide such apparatus which shall include means for securing and sealing the catheter that shall include only a unitary securing and sealing component that shall lend itself to ready manipulation by the surgeon during an implantation. Another object of this invention is to provide a set screw having unique application to organ-stimulating apparatus but also having more general use.